Articles | Volume 13, issue 5 
            
                
                    
            
            
            https://doi.org/10.5194/bg-13-1367-2016
                    © Author(s) 2016. This work is distributed under 
the Creative Commons Attribution 3.0 License.
                the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-13-1367-2016
                    © Author(s) 2016. This work is distributed under 
the Creative Commons Attribution 3.0 License.
                the Creative Commons Attribution 3.0 License.
Benthic phosphorus cycling in the Peruvian oxygen minimum zone
Ulrike Lomnitz
CORRESPONDING AUTHOR
                                            
                                    
                                            GEOMAR Helmholtz Centre for Ocean Research Kiel,
Wischhofstr. 1–3, 24148 Kiel, Germany
                                        
                                    Stefan Sommer
                                            GEOMAR Helmholtz Centre for Ocean Research Kiel,
Wischhofstr. 1–3, 24148 Kiel, Germany
                                        
                                    Andrew W. Dale
                                            GEOMAR Helmholtz Centre for Ocean Research Kiel,
Wischhofstr. 1–3, 24148 Kiel, Germany
                                        
                                    Carolin R. Löscher
                                            GEOMAR Helmholtz Centre for Ocean Research Kiel,
Wischhofstr. 1–3, 24148 Kiel, Germany
                                        
                                    Anna Noffke
                                            Institut für Seenforschung (ISF) der LUBW, Argenweg
50/1, 88085 Langenargen, Germany
                                        
                                    Klaus Wallmann
                                            GEOMAR Helmholtz Centre for Ocean Research Kiel,
Wischhofstr. 1–3, 24148 Kiel, Germany
                                        
                                    Christian Hensen
                                            GEOMAR Helmholtz Centre for Ocean Research Kiel,
Wischhofstr. 1–3, 24148 Kiel, Germany
                                        
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                                        Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen
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                                                The North Atlantic plays a crucial role in absorbing atmospheric CO2, but its air-sea CO2 flux varies across time and space. Using historical climate model simulations, we investigate how physical and oceanic processes drive the variability. Our results show that sea ice, temperature, salinity, wind stress, and ocean circulation shape CO2 exchange, with short-term fluctuations playing a dominant role. Understanding these complex interactions is key to predicting future ocean carbon uptake.
                                            
                                            
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                                    Preprint under review for ESSD 
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                                                Phosphorus is an essential element for life and its cycling strongly impact primary production. Here, we present a dataset of sediment-water fluxes of dissolved inorganic phosphorus from the Baltic Sea, an area with a long history of eutrophication. The fluxes were measured in situ with three types of benthic chamber landers at 59 stations over 20 years. The data show clear spatial patterns and will be important for marine management and studies on mechanisms in benthic phosphorus cycling.
                                            
                                            
                                        Isabell Schlangen, Elizabeth Leon-Palmero, Annabell Moser, Peihang Xu, Erik Laursen, and Carolin Regina Löscher
                                        EGUsphere, https://doi.org/10.5194/egusphere-2024-3680, https://doi.org/10.5194/egusphere-2024-3680, 2024
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                                        Sebastian I. Cantarero, Edgart Flores, Harry Allbrook, Paulina Aguayo, Cristian A. Vargas, John E. Tamanaha, J. Bentley C. Scholz, Lennart T. Bach, Carolin R. Löscher, Ulf Riebesell, Balaji Rajagopalan, Nadia Dildar, and Julio Sepúlveda
                                    Biogeosciences, 21, 3927–3958, https://doi.org/10.5194/bg-21-3927-2024, https://doi.org/10.5194/bg-21-3927-2024, 2024
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                                                Our study explores lipid remodeling in response to environmental stress, specifically how cell membrane chemistry changes. We focus on intact polar lipids in a phytoplankton community exposed to diverse stressors in a mesocosm experiment. The observed remodeling indicates acyl chain recycling for energy storage in intact polar lipids during stress, reallocating resources based on varying growth conditions. This understanding is essential to grasp the system's impact on cellular pools.
                                            
                                            
                                        Jakob Rønning, Zarah J. Kofoed, Mats Jacobsen, and Carolin R. Löscher
                                        EGUsphere, https://doi.org/10.5194/egusphere-2023-2884, https://doi.org/10.5194/egusphere-2023-2884, 2024
                                    Preprint archived 
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                                                In our study, we assessed the impact of olivine on marine primary producers of ocean-based solutions. The experiments revealed no negative effects on carbon fixation rates. Additions of the alkaline minerals did not establish growth inhibition; instead, they showed slight growth increases with species-specific responses. Ni exposure from olivine did not inhibit growth. However, limitations include the absence of responses in natural settings.
                                            
                                            
                                        Matthew D. Eisaman, Sonja Geilert, Phil Renforth, Laura Bastianini, James Campbell, Andrew W. Dale, Spyros Foteinis, Patricia Grasse, Olivia Hawrot, Carolin R. Löscher, Greg H. Rau, and Jakob Rønning
                                    State Planet, 2-oae2023, 3, https://doi.org/10.5194/sp-2-oae2023-3-2023, https://doi.org/10.5194/sp-2-oae2023-3-2023, 2023
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                                                Ocean-alkalinity-enhancement technologies refer to various methods and approaches aimed at increasing the alkalinity of seawater. This chapter explores technologies for increasing ocean alkalinity, including electrochemical-based approaches, ocean liming, accelerated weathering of limestone, hydrated carbonate addition, and coastal enhanced weathering, and suggests best practices in research and development.
                                            
                                            
                                        Ulf Riebesell, Daniela Basso, Sonja Geilert, Andrew W. Dale, and Matthias Kreuzburg
                                    State Planet, 2-oae2023, 6, https://doi.org/10.5194/sp-2-oae2023-6-2023, https://doi.org/10.5194/sp-2-oae2023-6-2023, 2023
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                                                Mesocosm experiments represent a highly valuable tool in determining the safe operating space of ocean alkalinity enhancement (OAE) applications. By combining realism and biological complexity with controllability and replication, they provide an ideal OAE test bed and a critical stepping stone towards field applications. Mesocosm approaches can also be helpful in testing the efficacy, efficiency and permanence of OAE applications.
                                            
                                            
                                        Zhibo Shao, Yangchun Xu, Hua Wang, Weicheng Luo, Lice Wang, Yuhong Huang, Nona Sheila R. Agawin, Ayaz Ahmed, Mar Benavides, Mikkel Bentzon-Tilia, Ilana Berman-Frank, Hugo Berthelot, Isabelle C. Biegala, Mariana B. Bif, Antonio Bode, Sophie Bonnet, Deborah A. Bronk, Mark V. Brown, Lisa Campbell, Douglas G. Capone, Edward J. Carpenter, Nicolas Cassar, Bonnie X. Chang, Dreux Chappell, Yuh-ling Lee Chen, Matthew J. Church, Francisco M. Cornejo-Castillo, Amália Maria Sacilotto Detoni, Scott C. Doney, Cecile Dupouy, Marta Estrada, Camila Fernandez, Bieito Fernández-Castro, Debany Fonseca-Batista, Rachel A. Foster, Ken Furuya, Nicole Garcia, Kanji Goto, Jesús Gago, Mary R. Gradoville, M. Robert Hamersley, Britt A. Henke, Cora Hörstmann, Amal Jayakumar, Zhibing Jiang, Shuh-Ji Kao, David M. Karl, Leila R. Kittu, Angela N. Knapp, Sanjeev Kumar, Julie LaRoche, Hongbin Liu, Jiaxing Liu, Caroline Lory, Carolin R. Löscher, Emilio Marañón, Lauren F. Messer, Matthew M. Mills, Wiebke Mohr, Pia H. Moisander, Claire Mahaffey, Robert Moore, Beatriz Mouriño-Carballido, Margaret R. Mulholland, Shin-ichiro Nakaoka, Joseph A. Needoba, Eric J. Raes, Eyal Rahav, Teodoro Ramírez-Cárdenas, Christian Furbo Reeder, Lasse Riemann, Virginie Riou, Julie C. Robidart, Vedula V. S. S. Sarma, Takuya Sato, Himanshu Saxena, Corday Selden, Justin R. Seymour, Dalin Shi, Takuhei Shiozaki, Arvind Singh, Rachel E. Sipler, Jun Sun, Koji Suzuki, Kazutaka Takahashi, Yehui Tan, Weiyi Tang, Jean-Éric Tremblay, Kendra Turk-Kubo, Zuozhu Wen, Angelicque E. White, Samuel T. Wilson, Takashi Yoshida, Jonathan P. Zehr, Run Zhang, Yao Zhang, and Ya-Wei Luo
                                    Earth Syst. Sci. Data, 15, 3673–3709, https://doi.org/10.5194/essd-15-3673-2023, https://doi.org/10.5194/essd-15-3673-2023, 2023
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                                                N2 fixation by marine diazotrophs is an important bioavailable N source to the global ocean. This updated global oceanic diazotroph database increases the number of in situ measurements of N2 fixation rates, diazotrophic cell abundances, and nifH gene copy abundances by 184 %, 86 %, and 809 %, respectively. Using the updated database, the global marine N2 fixation rate is estimated at 223 ± 30 Tg N yr−1, which triplicates that using the original database.
                                            
                                            
                                        Christian Furbo Reeder, Ina Stoltenberg, Jamileh Javidpour, and Carolin Regina Löscher
                                    Ocean Sci., 18, 401–417, https://doi.org/10.5194/os-18-401-2022, https://doi.org/10.5194/os-18-401-2022, 2022
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                                                The Baltic Sea is predicted to freshen in the future. To explore the effect of decreasing salinity on N2 fixers, we followed the natural salinity gradient in the Baltic Sea from the Kiel Fjord to the Gotland Basin and identified an N2 fixer community dominated by Nodularia and UCYN-A. A salinity threshold was identified at a salinity of 10, with Nodularia dominating at low and UCYN-A dominating at higher salinity, suggesting a future expansion of Nodularia N2 fixers and a retraction of UCYN-A.
                                            
                                            
                                        Carolin R. Löscher
                                    Biogeosciences, 18, 4953–4963, https://doi.org/10.5194/bg-18-4953-2021, https://doi.org/10.5194/bg-18-4953-2021, 2021
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                                                The Bay of Bengal (BoB) is classically seen as an ocean region with low primary production, which has been predicted to decrease even further. Here, the importance of such a trend is used to explore what could happen to the BoB's low-oxygen core waters if primary production decreases. Lower biological production leads to less oxygen loss in deeper waters by respiration; thus it could be that oxygen will not further decrease and the BoB will not become anoxic, different to other low-oxygen areas.
                                            
                                            
                                        Kai G. Schulz, Eric P. Achterberg, Javier Arístegui, Lennart T. Bach, Isabel Baños, Tim Boxhammer, Dirk Erler, Maricarmen Igarza, Verena Kalter, Andrea Ludwig, Carolin Löscher, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Elisabeth von der Esch, Bess B. Ward, and Ulf Riebesell
                                    Biogeosciences, 18, 4305–4320, https://doi.org/10.5194/bg-18-4305-2021, https://doi.org/10.5194/bg-18-4305-2021, 2021
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                                                Upwelling of nutrient-rich deep waters to the surface make eastern boundary upwelling systems hot spots of marine productivity. This leads to subsurface oxygen depletion and the transformation of bioavailable nitrogen into inert N2. Here we quantify nitrogen loss processes following a simulated deep water upwelling. Denitrification was the dominant process, and budget calculations suggest that a significant portion of nitrogen that could be exported to depth is already lost in the surface ocean.
                                            
                                            
                                        Siqi Wu, Moge Du, Xianhui Sean Wan, Corday Selden, Mar Benavides, Sophie Bonnet, Robert Hamersley, Carolin R. Löscher, Margaret R. Mulholland, Xiuli Yan, and Shuh-Ji Kao
                                        Biogeosciences Discuss., https://doi.org/10.5194/bg-2021-104, https://doi.org/10.5194/bg-2021-104, 2021
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                                                Nitrogen (N2) fixation is one of the most important nutrient sources to the ocean. Here, we report N2 fixation in the deep, dark ocean in the South China Sea via a highly sensitive new method and elaborate controls, showing the overlooked importance of N2 fixation in the deep ocean. By global data compilation, we also provide an easy measured basic parameter to estimate deep N2 fixation. Our study may help to expand the area limit of N2 fixation studies and better constrain global N2 fixation.
                                            
                                            
                                        Gerd Krahmann, Damian L. Arévalo-Martínez, Andrew W. Dale, Marcus Dengler, Anja Engel, Nicolaas Glock, Patricia Grasse, Johannes Hahn, Helena Hauss, Mark Hopwood, Rainer Kiko, Alexandra Loginova, Carolin R. Löscher, Marie Maßmig, Alexandra-Sophie Roy, Renato Salvatteci, Stefan Sommer, Toste Tanhua, and Hela Mehrtens
                                        Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2020-308, https://doi.org/10.5194/essd-2020-308, 2021
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                                                The project "Climate-Biogeochemistry Interactions in the Tropical Ocean" (SFB 754) was a multidisciplinary research project active from 2008 to 2019 aimed at a better understanding of the coupling between the tropical climate and ocean circulation and the ocean's oxygen and nutrient balance. On 34 research cruises, mainly in the Southeast Tropical Pacific and the Northeast Tropical Atlantic, 1071 physical, chemical and biological data sets were collected.
                                            
                                            
                                        Jan Lüdke, Marcus Dengler, Stefan Sommer, David Clemens, Sören Thomsen, Gerd Krahmann, Andrew W. Dale, Eric P. Achterberg, and Martin Visbeck
                                    Ocean Sci., 16, 1347–1366, https://doi.org/10.5194/os-16-1347-2020, https://doi.org/10.5194/os-16-1347-2020, 2020
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                                                We analyse the intraseasonal variability of the alongshore circulation off Peru in early 2017, this circulation is very important for the supply of nutrients to the upwelling regime. The causes of this variability and its impact on the biogeochemistry are investigated. The poleward flow is strengthened during the observed time period, likely by a downwelling coastal trapped wave. The stronger current causes an increase in nitrate and reduces the deficit of fixed nitrogen relative to phosphorus.
                                            
                                            
                                        Lennart Thomas Bach, Allanah Joy Paul, Tim Boxhammer, Elisabeth von der Esch, Michelle Graco, Kai Georg Schulz, Eric Achterberg, Paulina Aguayo, Javier Arístegui, Patrizia Ayón, Isabel Baños, Avy Bernales, Anne Sophie Boegeholz, Francisco Chavez, Gabriela Chavez, Shao-Min Chen, Kristin Doering, Alba Filella, Martin Fischer, Patricia Grasse, Mathias Haunost, Jan Hennke, Nauzet Hernández-Hernández, Mark Hopwood, Maricarmen Igarza, Verena Kalter, Leila Kittu, Peter Kohnert, Jesus Ledesma, Christian Lieberum, Silke Lischka, Carolin Löscher, Andrea Ludwig, Ursula Mendoza, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Joaquin Ortiz Cortes, Jonna Piiparinen, Claudia Sforna, Kristian Spilling, Sonia Sanchez, Carsten Spisla, Michael Sswat, Mabel Zavala Moreira, and Ulf Riebesell
                                    Biogeosciences, 17, 4831–4852, https://doi.org/10.5194/bg-17-4831-2020, https://doi.org/10.5194/bg-17-4831-2020, 2020
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                                                The eastern boundary upwelling system off Peru is among Earth's most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure.
                                            
                                            
                                        Alexandra N. Loginova, Andrew W. Dale, Frédéric A. C. Le Moigne, Sören Thomsen, Stefan Sommer, David Clemens, Klaus Wallmann, and Anja Engel
                                    Biogeosciences, 17, 4663–4679, https://doi.org/10.5194/bg-17-4663-2020, https://doi.org/10.5194/bg-17-4663-2020, 2020
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                                                We measured dissolved organic carbon (DOC), nitrogen (DON) and matter (DOM) optical properties in pore waters and near-bottom waters of the eastern tropical South Pacific off Peru. The difference between diffusion-driven and net fluxes of DOC and DON and qualitative changes in DOM optical properties suggested active microbial utilisation of the released DOM at the sediment–water interface. Our results suggest that the sediment release of DOM contributes to microbial processes in the area.
                                            
                                            
                                        Anna Plass, Christian Schlosser, Stefan Sommer, Andrew W. Dale, Eric P. Achterberg, and Florian Scholz
                                    Biogeosciences, 17, 3685–3704, https://doi.org/10.5194/bg-17-3685-2020, https://doi.org/10.5194/bg-17-3685-2020, 2020
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                                                We compare the cycling of Fe and Cd in sulfidic sediments of the Peruvian oxygen minimum zone. Due to the contrasting solubility of their sulfide minerals, the sedimentary Fe release and Cd burial fluxes covary with spatial and temporal distributions of H2S. Depending on the solubility of their sulfide minerals, sedimentary trace metal fluxes will respond differently to ocean deoxygenation/expansion of H2S concentrations, which may change trace metal stoichiometry of upwelling water masses.
                                            
                                            
                                        Sebastian Beil, Wolfgang Kuhnt, Ann Holbourn, Florian Scholz, Julian Oxmann, Klaus Wallmann, Janne Lorenzen, Mohamed Aquit, and El Hassane Chellai
                                    Clim. Past, 16, 757–782, https://doi.org/10.5194/cp-16-757-2020, https://doi.org/10.5194/cp-16-757-2020, 2020
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                                                Comparison of Cretaceous OAE1a and OAE2 in two drill cores with unusually high sedimentation rates shows that long-lasting negative δ13C excursions precede the positive δ13C excursions and that the evolution of the marine δ13C positive excursions is similar during both OAEs, although the durations of individual phases differ substantially. Phosphorus speciation data across OAE2 and the Mid-Cenomanian Event suggest a positive feedback loop, enhancing marine productivity during OAEs.
                                            
                                            
                                        Claudia Frey, Hermann W. Bange, Eric P. Achterberg, Amal Jayakumar, Carolin R. Löscher, Damian L. Arévalo-Martínez, Elizabeth León-Palmero, Mingshuang Sun, Xin Sun, Ruifang C. Xie, Sergey Oleynik, and Bess B. Ward
                                    Biogeosciences, 17, 2263–2287, https://doi.org/10.5194/bg-17-2263-2020, https://doi.org/10.5194/bg-17-2263-2020, 2020
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                                                The production of N2O via nitrification and denitrification associated with low-O2 waters is a major source of oceanic N2O. We investigated the regulation and dynamics of these processes with respect to O2 and organic matter inputs. The transcription of the key nitrification gene amoA rapidly responded to changes in O2 and strongly correlated with N2O production rates. N2O production by denitrification was clearly stimulated by organic carbon, implying that its supply controls N2O production.
                                            
                                            
                                        Sonja Geilert, Patricia Grasse, Kristin Doering, Klaus Wallmann, Claudia Ehlert, Florian Scholz, Martin Frank, Mark Schmidt, and Christian Hensen
                                    Biogeosciences, 17, 1745–1763, https://doi.org/10.5194/bg-17-1745-2020, https://doi.org/10.5194/bg-17-1745-2020, 2020
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                                                Marine silicate weathering is a key process of the marine silica cycle; however, its controlling processes are not well understood. In the Guaymas Basin, silicate weathering has been studied under markedly differing ambient conditions. Environmental settings like redox conditions or terrigenous input of reactive silicates appear to be major factors controlling marine silicate weathering. These factors need to be taken into account in future oceanic mass balances of Si and in modeling studies.
                                            
                                            
                                        Carolin R. Löscher, Wiebke Mohr, Hermann W. Bange, and Donald E. Canfield
                                    Biogeosciences, 17, 851–864, https://doi.org/10.5194/bg-17-851-2020, https://doi.org/10.5194/bg-17-851-2020, 2020
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                                                Oxygen minimum zones (OMZs) are ocean areas severely depleted in oxygen as a result of physical, chemical, and biological processes. Biologically, organic material is produced in the sea surface and exported to deeper waters, where it respires. In the Bay of Bengal (BoB), an OMZ is present, but there are traces of oxygen left. Our study now suggests that this is because one key process, nitrogen fixation, is absent in the BoB, thus preventing primary production and consecutive respiration.
                                            
                                            
                                        Tronje P. Kemena, Angela Landolfi, Andreas Oschlies, Klaus Wallmann, and Andrew W. Dale
                                    Earth Syst. Dynam., 10, 539–553, https://doi.org/10.5194/esd-10-539-2019, https://doi.org/10.5194/esd-10-539-2019, 2019
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                                                Oceanic deoxygenation is driven by climate change in several areas of the global ocean. Measurements indicate that ocean volumes with very low oxygen levels expand, with consequences for marine organisms and fishery. We found climate-change-driven phosphorus (P) input in the ocean is hereby an important driver for deoxygenation on longer timescales with effects in the next millennia.
                                            
                                            
                                        Sonja Geilert, Christian Hensen, Mark Schmidt, Volker Liebetrau, Florian Scholz, Mechthild Doll, Longhui Deng, Annika Fiskal, Mark A. Lever, Chih-Chieh Su, Stefan Schloemer, Sudipta Sarkar, Volker Thiel, and Christian Berndt
                                    Biogeosciences, 15, 5715–5731, https://doi.org/10.5194/bg-15-5715-2018, https://doi.org/10.5194/bg-15-5715-2018, 2018
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                                                Abrupt climate changes in Earth’s history might have been triggered by magmatic intrusions into organic-rich sediments, which can potentially release large amounts of greenhouse gases. In the Guaymas Basin, vigorous hydrothermal venting at the ridge axis and off-axis inactive vents show that magmatic intrusions are an effective way to release carbon but must be considered as very short-lived processes in a geological sense. These results need to be taken into account in  future climate models.
                                            
                                            
                                        Konstantin Stolpovsky, Andrew W. Dale, and Klaus Wallmann
                                    Biogeosciences, 15, 3391–3407, https://doi.org/10.5194/bg-15-3391-2018, https://doi.org/10.5194/bg-15-3391-2018, 2018
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                                                The paper describes a new way to parameterize G-type models in marine sediments using data about reactivity of organic carbon sinking to the seafloor.
                                            
                                            
                                        Johanna Maltby, Lea Steinle, Carolin R. Löscher, Hermann W. Bange, Martin A. Fischer, Mark Schmidt, and Tina Treude
                                    Biogeosciences, 15, 137–157, https://doi.org/10.5194/bg-15-137-2018, https://doi.org/10.5194/bg-15-137-2018, 2018
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                                                The activity and environmental controls of methanogenesis (MG) within the sulfate-reducing zone (0–30 cm below the seafloor) were investigated in organic-rich sediments of the seasonally hypoxic Eckernförde Bay, SW Baltic Sea. MG activity was mostly linked to non-competitive substrates. The major controls identified were organic matter availability, C / N, temperature, and O2 in the water column, revealing higher rates in warm, stratified, hypoxic seasons compared to colder, oxygenated seasons.
                                            
                                            
                                        Johannes Karstensen, Florian Schütte, Alice Pietri, Gerd Krahmann, Björn Fiedler, Damian Grundle, Helena Hauss, Arne Körtzinger, Carolin R. Löscher, Pierre Testor, Nuno Vieira, and Martin Visbeck
                                    Biogeosciences, 14, 2167–2181, https://doi.org/10.5194/bg-14-2167-2017, https://doi.org/10.5194/bg-14-2167-2017, 2017
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                                                High-resolution observational data from underwater gliders and ships are used to investigate drivers and pathways of nutrient upwelling in high-productive whirling ecosystems (eddies). The data suggest that the upwelling is created by the interaction of wind-induced internal waves with the local rotation of the eddy. Because of differences in nutrient and oxygen pathways, a low-oxygen core is established at shallow depth in the high-productive eddies.
                                            
                                            
                                        Björn Fiedler, Damian S. Grundle, Florian Schütte, Johannes Karstensen, Carolin R. Löscher, Helena Hauss, Hannes Wagner, Alexandra Loginova, Rainer Kiko, Péricles Silva, Toste Tanhua, and Arne Körtzinger
                                    Biogeosciences, 13, 5633–5647, https://doi.org/10.5194/bg-13-5633-2016, https://doi.org/10.5194/bg-13-5633-2016, 2016
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                                                Oxygen-depleted mesoscale features in the open eastern tropical North Atlantic, which are formed in the Mauritanian upwelling region, were discovered recently. This study examines biogeochemical structure and magnitudes of related processes within these isolated water masses. We found very low oxygen concentrations and strongly enhanced acidity at near-surface depth. Oxygen utilization and downward carbon export were found to exceed known values for this ocean region.
                                            
                                            
                                        Jessica Gier, Stefan Sommer, Carolin R. Löscher, Andrew W. Dale, Ruth A. Schmitz, and Tina Treude
                                    Biogeosciences, 13, 4065–4080, https://doi.org/10.5194/bg-13-4065-2016, https://doi.org/10.5194/bg-13-4065-2016, 2016
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                                                Benthic nitrogen fixation and sulfate reduction were investigated in the Peruvian oxygen minimum zone. The data suggest a coupling of both activities to a large extent, but that also sulfide and organic matter availability are controlling the benthic diazotrophy in this area. The molecular analysis confirms the presence of heterotrophic diazotrophs. This work improves our understanding of N cycling in OMZ sediments and the understanding of N sources in the marine environment.
                                            
                                            
                                        Carolin R. Löscher, Hermann W. Bange, Ruth A. Schmitz, Cameron M. Callbeck, Anja Engel, Helena Hauss, Torsten Kanzow, Rainer Kiko, Gaute Lavik, Alexandra Loginova, Frank Melzner, Judith Meyer, Sven C. Neulinger, Markus Pahlow, Ulf Riebesell, Harald Schunck, Sören Thomsen, and Hannes Wagner
                                    Biogeosciences, 13, 3585–3606, https://doi.org/10.5194/bg-13-3585-2016, https://doi.org/10.5194/bg-13-3585-2016, 2016
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                                                The ocean loses oxygen due to climate change. Addressing this issue in tropical ocean regions (off Peru and Mauritania), we aimed to understand the effects of oxygen depletion on various aspects of marine biogeochemistry, including primary production and export production, the nitrogen cycle, greenhouse gas production, organic matter fluxes and remineralization, and the role of zooplankton and viruses.
                                            
                                            
                                        Pei-Chuan Chuang, Megan B. Young, Andrew W. Dale, Laurence G. Miller, Jorge A. Herrera-Silveira, and Adina Paytan
                                    Biogeosciences, 13, 2981–3001, https://doi.org/10.5194/bg-13-2981-2016, https://doi.org/10.5194/bg-13-2981-2016, 2016
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                                                A transport-reaction model was used to simulate porewater methane and sulfate concentrations. Model results and sediment slurry incubation experiments show high methane production rates supported by non-competitive substrates and ample dissolved and labile organic matter as well as methane from deeper sediment through bubbles dissolution and diffusion. The shallow methane production and accumulation depths in these sediments promote high methane fluxes to the water column and atmosphere.
                                            
                                            
                                        Carolin R. Löscher, Annie Bourbonnais, Julien Dekaezemacker, Chawalit N. Charoenpong, Mark A. Altabet, Hermann W. Bange, Rena Czeschel, Chris Hoffmann, and Ruth Schmitz
                                    Biogeosciences, 13, 2889–2899, https://doi.org/10.5194/bg-13-2889-2016, https://doi.org/10.5194/bg-13-2889-2016, 2016
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                                                The ocean is full of eddies and they play a key role for ocean biogeochemistry. In order to understand dinitrogen (N2) fixation, one major control of oceanic primary production, we investigated three eddies in the eastern tropical South Pacific off Peru. We conducted the first detailed survey and found increased N2 fixation in the oxygen-depleted cores of anticyclonic mode water eddies. Taken together, we could – for the first time – show that eddies play an important role in N2 fixation off Peru.
                                            
                                            
                                        Helena Hauss, Svenja Christiansen, Florian Schütte, Rainer Kiko, Miryam Edvam Lima, Elizandro Rodrigues, Johannes Karstensen, Carolin R. Löscher, Arne Körtzinger, and Björn Fiedler
                                    Biogeosciences, 13, 1977–1989, https://doi.org/10.5194/bg-13-1977-2016, https://doi.org/10.5194/bg-13-1977-2016, 2016
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                                                In a low-oxygen eddy in the tropical Atlantic, total zooplankton biomass was increased.  Larger plankton avoided the oxygen minimum zone (OMZ, < 20 µmol O2 kg−1). We identified four strategies by different plankton groups: (i) shallow OMZ avoidance and compression at surface, (ii) migration to shallow OMZ core during daytime, migration to surface at nighttime, (iii) residing in shallow OMZ day and night and (iv) migration through the shallow OMZ from oxygenated depths to surface and back.
                                            
                                            
                                        Lorenzo Rovelli, Marcus Dengler, Mark Schmidt, Stefan Sommer, Peter Linke, and Daniel F. McGinnis
                                    Biogeosciences, 13, 1609–1620, https://doi.org/10.5194/bg-13-1609-2016, https://doi.org/10.5194/bg-13-1609-2016, 2016
                            Damian L. Arévalo-Martínez, Annette Kock, Carolin R. Löscher, Ruth A. Schmitz, Lothar Stramma, and Hermann W. Bange
                                    Biogeosciences, 13, 1105–1118, https://doi.org/10.5194/bg-13-1105-2016, https://doi.org/10.5194/bg-13-1105-2016, 2016
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                                                We present the first measurements of N2O across three mesoscale eddies in the eastern tropical South Pacific. Eddie's vertical structure, offshore transport, properties during its formation and near-surface primary production determined the N2O distribution. Substantial depletion of N2O within the core of anticyclonic eddies suggests that although these are transient features, N-loss processes within their centres can lead to an enhanced N2O sink which is not accounted for in marine N2O budgets.
                                            
                                            
                                        K. Wallmann, B. Schneider, and M. Sarnthein
                                    Clim. Past, 12, 339–375, https://doi.org/10.5194/cp-12-339-2016, https://doi.org/10.5194/cp-12-339-2016, 2016
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                                                An Earth system model was set up and applied to evaluate the effects of sea-level change, ocean dynamics, and nutrient utilization on seawater composition and atmospheric pCO2  over the last glacial cycle. The model results strongly suggest that global sea-level change contributed significantly to the slow glacial decline in atmospheric pCO2  and the gradual pCO2  increase over the Holocene whereas the rapid deglacial pCO2  rise was induced by fast changes in ocean dynamics and nutrient utilization.
                                            
                                            
                                        A. Kock, D. L. Arévalo-Martínez, C. R. Löscher, and H. W. Bange
                                    Biogeosciences, 13, 827–840, https://doi.org/10.5194/bg-13-827-2016, https://doi.org/10.5194/bg-13-827-2016, 2016
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                                                We measured the nitrous oxide (N2O) distribution in the water column in the oxygen minimum zone off Peru, an area with extremely high N2O emissions. Our data show very variable and often very high N2O concentrations in the water column at the coast, which lead to high N2O emissions when these waters are brought to the surface. The very high N2O production off Peru may be caused by high nutrient turnover rates together with rapid changes in the oxygen concentrations.
                                            
                                            
                                        J. Meyer, C. R. Löscher, S. C. Neulinger, A. F. Reichel, A. Loginova, C. Borchard, R. A. Schmitz, H. Hauss, R. Kiko, and U. Riebesell
                                    Biogeosciences, 13, 781–794, https://doi.org/10.5194/bg-13-781-2016, https://doi.org/10.5194/bg-13-781-2016, 2016
                            J. Maltby, S. Sommer, A. W. Dale, and T. Treude
                                    Biogeosciences, 13, 283–299, https://doi.org/10.5194/bg-13-283-2016, https://doi.org/10.5194/bg-13-283-2016, 2016
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                                                The concurrence of methanogenesis and sulfate reduction was investigated in surface sediments (0–25cm b.s.f.) traversing the Peruvian margin. Surface methanogenesis was mainly based on non-competitive substrates to avoid competition with sulfate reducers. Accordingly, surface methanogenesis was mainly controlled by the availability of labile organic matter. The high relevance of surface methanogenesis especially on the shelf indicates its underestimated role within benthic methane budgeting.
                                            
                                            
                                        C. R. Löscher, M. A. Fischer, S. C. Neulinger, B. Fiedler, M. Philippi, F. Schütte, A. Singh, H. Hauss, J. Karstensen, A. Körtzinger, S. Künzel, and R. A. Schmitz
                                    Biogeosciences, 12, 7467–7482, https://doi.org/10.5194/bg-12-7467-2015, https://doi.org/10.5194/bg-12-7467-2015, 2015
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                                                The waters of the tropical Atlantic Open Ocean usually contain comparably high concentrations of oxygen. Now, it became clear that there are watermasses related to eddies that are nearly anoxic. We surveyed one of those eddies and found a biosphere that largely differed from the usual biosphere present in this area with a specific community responsible for primary production and for degradation processes. Further, we found the very first indication for active nitrogen loss in the open Atlantic.
                                            
                                            
                                        P. Steeb, S. Krause, P. Linke, C. Hensen, A. W. Dale, M. Nuzzo, and T. Treude
                                    Biogeosciences, 12, 6687–6706, https://doi.org/10.5194/bg-12-6687-2015, https://doi.org/10.5194/bg-12-6687-2015, 2015
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                                                We combined field, laboratory (sediment-flow-through system) and numerical modeling work to investigate cold seep sediments at Quespos Slide, offshore of Costa Rica. The results demonstrated the efficiency of the benthic methane filter and provided an estimate for its response time (ca. 170 days) to changes in fluid fluxes.
                                            
                                            
                                        A. W. Dale, S. Sommer, U. Lomnitz, I. Montes, T. Treude, V. Liebetrau, J. Gier, C. Hensen, M. Dengler, K. Stolpovsky, L. D. Bryant, and K. Wallmann
                                    Biogeosciences, 12, 1537–1559, https://doi.org/10.5194/bg-12-1537-2015, https://doi.org/10.5194/bg-12-1537-2015, 2015
                            J. Friedrich, F. Janssen, D. Aleynik, H. W. Bange, N. Boltacheva, M. N. Çagatay, A. W. Dale, G. Etiope, Z. Erdem, M. Geraga, A. Gilli, M. T. Gomoiu, P. O. J. Hall, D. Hansson, Y. He, M. Holtappels, M. K. Kirf, M. Kononets, S. Konovalov, A. Lichtschlag, D. M. Livingstone, G. Marinaro, S. Mazlumyan, S. Naeher, R. P. North, G. Papatheodorou, O. Pfannkuche, R. Prien, G. Rehder, C. J. Schubert, T. Soltwedel, S. Sommer, H. Stahl, E. V. Stanev, A. Teaca, A. Tengberg, C. Waldmann, B. Wehrli, and F. Wenzhöfer
                                    Biogeosciences, 11, 1215–1259, https://doi.org/10.5194/bg-11-1215-2014, https://doi.org/10.5194/bg-11-1215-2014, 2014
                            S. Krause, P. Steeb, C. Hensen, V. Liebetrau, A. W. Dale, M. Nuzzo, and T. Treude
                                    Biogeosciences, 11, 507–523, https://doi.org/10.5194/bg-11-507-2014, https://doi.org/10.5194/bg-11-507-2014, 2014
                            N. Glock, J. Schönfeld, A. Eisenhauer, C. Hensen, J. Mallon, and S. Sommer
                                    Biogeosciences, 10, 4767–4783, https://doi.org/10.5194/bg-10-4767-2013, https://doi.org/10.5194/bg-10-4767-2013, 2013
                            V. J. Bertics, C. R. Löscher, I. Salonen, A. W. Dale, J. Gier, R. A. Schmitz, and T. Treude
                                    Biogeosciences, 10, 1243–1258, https://doi.org/10.5194/bg-10-1243-2013, https://doi.org/10.5194/bg-10-1243-2013, 2013
                            A. W. Dale, V. J. Bertics, T. Treude, S. Sommer, and K. Wallmann
                                    Biogeosciences, 10, 629–651, https://doi.org/10.5194/bg-10-629-2013, https://doi.org/10.5194/bg-10-629-2013, 2013
                            K. Soetaert, D. van Oevelen, and S. Sommer
                                    Biogeosciences, 9, 5341–5352, https://doi.org/10.5194/bg-9-5341-2012, https://doi.org/10.5194/bg-9-5341-2012, 2012
                            Related subject area
            Biogeochemistry: Sediment
            
                    
                        
                            
                            
                                     
                                Faithful transfer of radiolarian silicon isotope signatures from water column to sediments in the South China Sea
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Ancient clays support contemporary biogeochemical activity in the Critical Zone
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Organic carbon, mercury, and sediment characteristics along a land–shore transect in Arctic Alaska
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                            
                                     
                                Impacts of recent eutrophication and deoxygenation on the sediment biogeochemistry in the Sea of Marmara
                                
                                        
                                            
                                    
                            
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Dissolved Mn(III) is a key redox intermediate in sediments of a seasonally euxinic coastal basin
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Unexpected scarcity of ANME archaea in hydrocarbon seeps within Monterey Bay
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Reviews and syntheses: Tufa microbialites on rocky coasts – towards an integrated terminology
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Seafloor sediment characterization improves estimates of organic carbon standing stocks: an example from the Eastern Shore Islands, Nova Scotia, Canada
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                How is particulate organic carbon transported through the river-fed submarine Congo Canyon to the deep sea?
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                The fate of fixed nitrogen in Santa Barbara Basin sediments during seasonal anoxia
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Distinct oxygenation modes of the Gulf of Oman over the past 43 000 years – a multi-proxy approach
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Potential impacts of cable bacteria activity on hard-shelled benthic foraminifera: implications for their interpretation as bioindicators or paleoproxies
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Evidence of cryptic methane cycling and non-methanogenic methylamine consumption in the sulfate-reducing zone of sediment in the Santa Barbara Basin, California
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Assessing global-scale organic matter reactivity patterns in marine sediments using a lognormal reactive continuum model
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Deposit-feeding of Nonionellina labradorica (foraminifera) from an Arctic methane seep site and possible association with a methanotroph
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Benthic silicon cycling in the Arctic Barents Sea: a reaction–transport model study
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Long-term incubations provide insight into the mechanisms of anaerobic oxidation of methane in methanogenic lake sediments
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Ideas and perspectives: Sea-level change, anaerobic methane oxidation, and the glacial–interglacial phosphorus cycle
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Estimation of the natural background of phosphate in a lowland river using tidal marsh sediment cores
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Geochemical consequences of oxygen diffusion from the oceanic crust into overlying sediments and its significance for biogeochemical cycles based on sediments of the northeast Pacific
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Carbon sources of benthic fauna in temperate lakes across multiple trophic states
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Bioturbation has a limited effect on phosphorus burial in salt marsh sediments
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Biogeochemical impact of cable bacteria on coastal Black Sea sediment
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Organic carbon characteristics in ice-rich permafrost in alas and Yedoma deposits, central Yakutia, Siberia
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                The control of hydrogen sulfide on benthic iron and cadmium fluxes in the oxygen minimum zone off Peru
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Quantity and distribution of methane entrapped in sediments of calcareous, Alpine glacier forefields
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Assessing the potential for non-turbulent methane escape from the East Siberian Arctic Shelf
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Vertical transport of sediment-associated metals and cyanobacteria by ebullition in a stratified lake
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Evidence of changes in sedimentation rate and sediment fabric in a low-oxygen setting: Santa Monica Basin, CA
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Authigenic formation of Ca–Mg carbonates in the shallow alkaline Lake Neusiedl, Austria
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Vivianite formation in ferruginous sediments from Lake Towuti, Indonesia
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Impact of ambient conditions on the Si isotope fractionation in marine pore fluids during early diagenesis
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Impact of small-scale disturbances on geochemical conditions, biogeochemical processes and element fluxes in surface sediments of the eastern Clarion–Clipperton Zone, Pacific Ocean
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Acetate turnover and methanogenic pathways in Amazonian lake sediments
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Benthic alkalinity and dissolved inorganic carbon fluxes in the Rhône River prodelta generated by decoupled aerobic and anaerobic processes
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Small-scale heterogeneity of trace metals including rare earth elements and yttrium in deep-sea sediments and porewaters of the Peru Basin, southeastern equatorial Pacific
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Organic matter contents and degradation in a highly trawled area during fresh particle inputs (Gulf of Castellammare, southwestern Mediterranean)
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Identifying the core bacterial microbiome of hydrocarbon degradation and a shift of dominant methanogenesis pathways in the oil and aqueous phases of petroleum reservoirs of different temperatures from China
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Effects of eutrophication on sedimentary organic carbon cycling in five temperate lakes
                                
                            
                        
                    
                    
                        
                            
                            
                                     
                                Evidence for microbial iron reduction in the methanic sediments of the oligotrophic southeastern Mediterranean continental shelf
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Hydrothermal alteration of aragonitic biocarbonates: assessment of micro- and nanostructural dissolution–reprecipitation and constraints of diagenetic overprint from quantitative statistical grain-area analysis
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Large variations in iron input to an oligotrophic Baltic Sea estuary: impact on sedimentary phosphorus burial
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Vivianite formation in methane-rich deep-sea sediments from the South China Sea
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                                     
                                Benthic archaea as potential sources of tetraether membrane lipids in sediments across an oxygen minimum zone
                                
                                        
                                            
                                    
                            
                            
                        
                    
                    
                        
                            
                            
                            
                                     
                                Carbon amendment stimulates benthic nitrogen cycling during the bioremediation of particulate aquaculture waste
                                
                                        
                                            
                                    
                            
                            
                            
                        
                    
                    
                        
                            
                            
                            
                                     
                                Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes
                                
                                        
                                            
                                    
                            
                            
                            
                        
                    
                    
                        
                            
                            
                            
                                     
                                Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment
                                
                                        
                                            
                                    
                            
                            
                            
                        
                    
                    
            
        
        Qiang Zhang, George E. A. Swann, Vanessa Pashley, and Matthew S. A. Horstwood
                                    Biogeosciences, 22, 3533–3546, https://doi.org/10.5194/bg-22-3533-2025, https://doi.org/10.5194/bg-22-3533-2025, 2025
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                                                We present the first coupled record of radiolarian silicon isotopes (δ30Sirad) from paired water column and surface sediment samples, along with the fractionation factor for δ30Sirad in the South China Sea. No significant discrepancies in δ30Sirad values were observed between plankton and sediment samples, implying minimal dissolution impact on δ30Sirad during sinking. This indicates faithful preservation of the δ30Sirad signature and its potential for studying past marine silicon cycle changes.
                                            
                                            
                                        Vanessa M. Alfonso, Peter M. Groffman, Zhongqi Cheng, and David E. Seidemann
                                    Biogeosciences, 22, 3357–3373, https://doi.org/10.5194/bg-22-3357-2025, https://doi.org/10.5194/bg-22-3357-2025, 2025
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                                                Major questions in Critical Zone science center on the ability of ancient materials to support biogeochemical processes related to the cycling of carbon and nitrogen. This study sought to explore organomineral interactions by investigating the functional performance of clays through measurements of biogeochemical processes occurring on these materials.  Results indicate that ancient clays are contributing to contemporary Critical Zone biogeochemical processes at ecosystem and landscape scales. 
                                            
                                            
                                        Frieda P. Giest, Maren Jenrich, Guido Grosse, Benjamin M. Jones, Kai Mangelsdorf, Torben Windirsch, and Jens Strauss
                                    Biogeosciences, 22, 2871–2887, https://doi.org/10.5194/bg-22-2871-2025, https://doi.org/10.5194/bg-22-2871-2025, 2025
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                                                Climate warming causes permafrost to thaw, releasing greenhouse gases and affecting ecosystems. We studied sediments from Arctic coastal landscapes, including land, lakes, lagoons, and the ocean, finding that organic carbon storage and quality vary with landscape features and saltwater influence. Freshwater and land areas store more carbon, while saltwater reduces its quality. These findings improve predictions of Arctic responses to climate change and their impact on global carbon cycling.
                                            
                                            
                                        İsmail Akçay, Süleyman Tuğrul, Hasan Örek, Devrim Tezcan, Koray Özhan, Barış Salihoğlu, and Mustafa Yücel
                                        EGUsphere, https://doi.org/10.5194/egusphere-2025-1255, https://doi.org/10.5194/egusphere-2025-1255, 2025
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                                                This study aims to understand the impacts of deoxygenation and coastal eutrophication on sedimentary biogeochemical processes in the Marmara Sea. Our results showed that the dynamics of porewater nutrients, redox-sensitive elements, major ions involved in the diagenetic processes and also solid-state geochemistry in the Marmara Sea have been influenced by eutrophication and bottom water hypoxia/anoxia.
                                            
                                            
                                        Ellen Schnabel, Aurèle Vuillemin, Cédric C. Laczny, Benoit J. Kunath, André R. Soares, Alexander J. Probst, Rolando Di Primio, Jens Kallmeyer, and the PROSPECTOMICS Consortium
                                    Biogeosciences, 22, 767–784, https://doi.org/10.5194/bg-22-767-2025, https://doi.org/10.5194/bg-22-767-2025, 2025
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                                                This study analysed marine sediment samples from areas with and without minimal hydrocarbon seepage from reservoirs underneath. Depth profiles of dissolved chemical components in the pore water and molecular biological data revealed differences in microbial community composition and activity. These results indicate that even minor hydrocarbon seepage affects sedimentary biogeochemical cycling in marine sediments, potentially providing a new tool for the detection of hydrocarbon reservoirs.
                                            
                                            
                                        Robin Klomp, Olga M. Żygadłowska, Mike S. M. Jetten, Véronique E. Oldham, Niels A. G. M. van Helmond, Caroline P. Slomp, and Wytze K. Lenstra
                                    Biogeosciences, 22, 751–765, https://doi.org/10.5194/bg-22-751-2025, https://doi.org/10.5194/bg-22-751-2025, 2025
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                                                In marine sediments, dissolved Mn is present as either Mn(III) or Mn(II). We apply a reactive transport model to geochemical data for a seasonally anoxic and sulfidic coastal basin to determine the pathways of formation and removal of dissolved Mn(III) in the sediment. We demonstrate a critical role for reactions with Fe(II) and show evidence for substantial benthic release of dissolved Mn(III). Given the mobility of Mn(III), these findings have important implications for marine Mn cycling.
                                            
                                            
                                        Amanda C. Semler and Anne E. Dekas
                                    Biogeosciences, 22, 385–403, https://doi.org/10.5194/bg-22-385-2025, https://doi.org/10.5194/bg-22-385-2025, 2025
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                                                Marine hydrocarbon seeps typically host subsurface microorganisms capable of degrading methane before it is emitted to the water column. Here we describe a seep in Monterey Bay which virtually lacks known methanotrophs and where biological consumption of methane at depth is undetected. Our findings suggest that some seeps are missing this critical biofilter and that seeps may be a more significant source of methane to the water column than previously realized.
                                            
                                            
                                        Thomas W. Garner, J. Andrew G. Cooper, Alan M. Smith, Gavin M. Rishworth, and Matt Forbes
                                    Biogeosciences, 21, 4785–4807, https://doi.org/10.5194/bg-21-4785-2024, https://doi.org/10.5194/bg-21-4785-2024, 2024
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                                                There is a diverse and often conflicting suite of terminologies, classifications, and nomenclature applicable to the study of terrestrial carbonate deposits and microbialites (deposits that wholly or primarily accrete as a result of microbial activity). We review existing schemes, identify duplication and redundancy, and present a new integrated approach applicable to tufa microbialites on rock coasts.
                                            
                                            
                                        Catherine Brenan, Markus Kienast, Vittorio Maselli, Christopher K. Algar, Benjamin Misiuk, and Craig J. Brown
                                    Biogeosciences, 21, 4569–4586, https://doi.org/10.5194/bg-21-4569-2024, https://doi.org/10.5194/bg-21-4569-2024, 2024
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                                                Quantifying how much organic carbon is stored in seafloor sediments is key to assessing how human activities can accelerate the process of carbon storage at the seabed, an important consideration for climate change. This study uses seafloor sediment maps to model organic carbon content. Carbon estimates were 12 times higher when assuming the absence of detailed sediment maps, demonstrating that high-resolution seafloor mapping is critically important for improved estimates of organic carbon.
                                            
                                            
                                        Sophie Hage, Megan L. Baker, Nathalie Babonneau, Guillaume Soulet, Bernard Dennielou, Ricardo Silva Jacinto, Robert G. Hilton, Valier Galy, François Baudin, Christophe Rabouille, Clément Vic, Sefa Sahin, Sanem Açikalin, and Peter J. Talling
                                    Biogeosciences, 21, 4251–4272, https://doi.org/10.5194/bg-21-4251-2024, https://doi.org/10.5194/bg-21-4251-2024, 2024
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                                                The land-to-ocean flux of particulate organic carbon (POC) is difficult to measure, inhibiting accurate modeling of the global carbon cycle. Here, we quantify the POC flux between one of the largest rivers on Earth (Congo) and the ocean. POC in the form of vegetation and soil is transported by episodic submarine avalanches in a 1000 km long canyon at up to 5 km water depth. The POC flux induced by avalanches is at least 3 times greater than that induced by the background flow related to tides.
                                            
                                            
                                        Xuefeng Peng, David J. Yousavich, Annie Bourbonnais, Frank Wenzhöfer, Felix Janssen, Tina Treude, and David L. Valentine
                                    Biogeosciences, 21, 3041–3052, https://doi.org/10.5194/bg-21-3041-2024, https://doi.org/10.5194/bg-21-3041-2024, 2024
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                                                Biologically available (fixed) nitrogen (N) is a limiting nutrient for life in the ocean. Under low-oxygen conditions, fixed N is either removed via denitrification or retained via dissimilatory nitrate reduction to ammonia (DNRA). Using in situ incubations in the Santa Barbara Basin, which undergoes seasonal anoxia, we found that benthic denitrification was the dominant nitrate reduction process, while nitrate availability and organic carbon content control the relative importance of DNRA.
                                            
                                            
                                        Nicole Burdanowitz, Gerhard Schmiedl, Birgit Gaye, Philipp M. Munz, and Hartmut Schulz
                                    Biogeosciences, 21, 1477–1499, https://doi.org/10.5194/bg-21-1477-2024, https://doi.org/10.5194/bg-21-1477-2024, 2024
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                                                We analyse benthic foraminifera, nitrogen isotopes and lipids in a sediment core from the Gulf of Oman to investigate how the oxygen minimum zone (OMZ) and bottom water (BW) oxygenation have reacted to climatic changes since 43 ka. The OMZ and BW deoxygenation was strong during the Holocene, but the OMZ was well ventilated during the LGM period. We found an unstable mode of oscillating oxygenation states, from moderately oxygenated in cold stadials to deoxygenated in warm interstadials in MIS 3.
                                            
                                            
                                        Maxime Daviray, Emmanuelle Geslin, Nils Risgaard-Petersen, Vincent V. Scholz, Marie Fouet, and Edouard Metzger
                                    Biogeosciences, 21, 911–928, https://doi.org/10.5194/bg-21-911-2024, https://doi.org/10.5194/bg-21-911-2024, 2024
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                                                Coastal marine sediments are subject to major acidification processes because of climate change and human activities, but these processes can also result from biotic activity. We studied the sediment acidifcation effect on benthic calcareous foraminifera in intertidal mudflats. The strong pH decrease in sediments probably caused by cable bacteria led to calcareous test dissolution of living and dead foraminifera, threatening the test preservation and their robustness as environmental proxies.
                                            
                                            
                                        Sebastian J. E. Krause, Jiarui Liu, David J. Yousavich, DeMarcus Robinson, David W. Hoyt, Qianhui Qin, Frank Wenzhöfer, Felix Janssen, David L. Valentine, and Tina Treude
                                    Biogeosciences, 20, 4377–4390, https://doi.org/10.5194/bg-20-4377-2023, https://doi.org/10.5194/bg-20-4377-2023, 2023
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                                                Methane is a potent greenhouse gas, and hence it is important to understand its sources and sinks in the environment. Here we present new data from organic-rich surface sediments below an oxygen minimum zone off the coast of California (Santa Barbara Basin) demonstrating the simultaneous microbial production and consumption of methane, which appears to be an important process preventing the build-up of methane in these sediments and the emission into the water column and atmosphere.
                                            
                                            
                                        Sinan Xu, Bo Liu, Sandra Arndt, Sabine Kasten, and Zijun Wu
                                    Biogeosciences, 20, 2251–2263, https://doi.org/10.5194/bg-20-2251-2023, https://doi.org/10.5194/bg-20-2251-2023, 2023
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                                                We use a reactive continuum model based on a lognormal distribution (l-RCM) to inversely determine model parameters μ and σ at 123 sites across the global ocean. Our results show organic matter (OM) reactivity is more than 3 orders of magnitude higher in shelf than in abyssal regions. In addition, OM reactivity is higher than predicted in some specific regions, yet the l-RCM can still capture OM reactivity features in these regions.
                                            
                                            
                                        Christiane Schmidt, Emmanuelle Geslin, Joan M. Bernhard, Charlotte LeKieffre, Mette Marianne Svenning, Helene Roberge, Magali Schweizer, and Giuliana Panieri
                                    Biogeosciences, 19, 3897–3909, https://doi.org/10.5194/bg-19-3897-2022, https://doi.org/10.5194/bg-19-3897-2022, 2022
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                                                This study is the first to show non-selective deposit feeding in the foraminifera Nonionella labradorica and the possible uptake of methanotrophic bacteria. We carried out a feeding experiment with a marine methanotroph to examine the ultrastructure of the cell and degradation vacuoles using transmission electron microscopy (TEM). The results revealed three putative methanotrophs at the outside of the cell/test, which could be taken up via non-targeted grazing in seeps or our experiment.
                                            
                                            
                                        James P. J. Ward, Katharine R. Hendry, Sandra Arndt, Johan C. Faust, Felipe S. Freitas, Sian F. Henley, Jeffrey W. Krause, Christian März, Allyson C. Tessin, and Ruth L. Airs
                                    Biogeosciences, 19, 3445–3467, https://doi.org/10.5194/bg-19-3445-2022, https://doi.org/10.5194/bg-19-3445-2022, 2022
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                                                The seafloor plays an important role in the cycling of silicon (Si), a key nutrient that promotes marine primary productivity. In our model study, we disentangle major controls on the seafloor Si cycle to better anticipate the impacts of continued warming and sea ice melt in the Barents Sea. We uncover a coupling of the iron redox and Si cycles, dissolution of lithogenic silicates, and authigenic clay formation, comprising a Si sink that could have implications for the Arctic Ocean Si budget.
                                            
                                            
                                        Hanni Vigderovich, Werner Eckert, Michal Elul, Maxim Rubin-Blum, Marcus Elvert, and Orit Sivan
                                    Biogeosciences, 19, 2313–2331, https://doi.org/10.5194/bg-19-2313-2022, https://doi.org/10.5194/bg-19-2313-2022, 2022
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                                                Anaerobic oxidation of methane (AOM) is one of the major processes limiting the release of the greenhouse gas methane from natural environments. Here we show that significant AOM exists in the methane zone of lake sediments in natural conditions and even after long-term (ca. 18 months) anaerobic slurry incubations with two stages. Methanogens were most likely responsible for oxidizing the methane, and humic substances and iron oxides are likely electron acceptors to support this oxidation.
                                            
                                            
                                        Bjorn Sundby, Pierre Anschutz, Pascal Lecroart, and Alfonso Mucci
                                    Biogeosciences, 19, 1421–1434, https://doi.org/10.5194/bg-19-1421-2022, https://doi.org/10.5194/bg-19-1421-2022, 2022
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                                                A glacial–interglacial methane-fuelled redistribution of reactive phosphorus between the oceanic and sedimentary phosphorus reservoirs can occur in the ocean when falling sea level lowers the pressure on the seafloor, destabilizes methane hydrates, and triggers the dissolution of P-bearing iron oxides. The mass of phosphate potentially mobilizable from the sediment is similar to the size of the current oceanic reservoir. Hence, this process may play a major role in the marine phosphorus cycle.
                                            
                                            
                                        Florian Lauryssen, Philippe Crombé, Tom Maris, Elliot Van Maldegem, Marijn Van de Broek, Stijn Temmerman, and Erik Smolders
                                    Biogeosciences, 19, 763–776, https://doi.org/10.5194/bg-19-763-2022, https://doi.org/10.5194/bg-19-763-2022, 2022
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                                                Surface waters in lowland regions have a poor surface water quality, mainly due to excess nutrients like phosphate. Therefore, we wanted to know the phosphate levels without humans, also called the pre-industrial background. Phosphate binds strongly to sediment particles, suspended in the river water. In this research we used sediments deposited by a river as an archive for surface water phosphate back to 1800 CE. Pre-industrial phosphate levels were estimated at one-third of the modern levels.
                                            
                                            
                                        Gerard J. M. Versteegh, Andrea Koschinsky, Thomas Kuhn, Inken Preuss, and Sabine Kasten
                                    Biogeosciences, 18, 4965–4984, https://doi.org/10.5194/bg-18-4965-2021, https://doi.org/10.5194/bg-18-4965-2021, 2021
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                                                Oxygen penetrates sediments not only from the ocean bottom waters but also from the basement. The impact of the latter is poorly understood. We show that this basement oxygen has a clear impact on the nitrogen cycle, the redox state, and the distribution of manganese, nickel cobalt and organic matter in the sediments. This is important for (1) global biogeochemical cycles, (2) understanding sedimentary life and (3) the interpretation of the sediment record to reconstruct the past.
                                            
                                            
                                        Annika Fiskal, Eva Anthamatten, Longhui Deng, Xingguo Han, Lorenzo Lagostina, Anja Michel, Rong Zhu, Nathalie Dubois, Carsten J. Schubert, Stefano M. Bernasconi, and Mark A. Lever
                                    Biogeosciences, 18, 4369–4388, https://doi.org/10.5194/bg-18-4369-2021, https://doi.org/10.5194/bg-18-4369-2021, 2021
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                                                Microbially produced methane can serve as a carbon source for freshwater macrofauna most likely through grazing on methane-oxidizing bacteria. This study investigates the contributions of different carbon sources to macrofaunal biomass. Our data suggest that the average contribution of methane-derived carbon is similar between different fauna but overall remains low. This is further supported by the low abundance of methane-cycling microorganisms.
                                            
                                            
                                        Astrid Hylén, Sebastiaan J. van de Velde, Mikhail Kononets, Mingyue Luo, Elin Almroth-Rosell, and Per O. J. Hall
                                    Biogeosciences, 18, 2981–3004, https://doi.org/10.5194/bg-18-2981-2021, https://doi.org/10.5194/bg-18-2981-2021, 2021
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                                                Sediments in oxygen-depleted ocean areas release high amounts of phosphorus, feeding algae that consume oxygen upon degradation, leading to further phosphorus release. Oxygenation is thought to trap phosphorus in the sediment and break this feedback. We studied the sediment phosphorus cycle in a previously anoxic area after an inflow of oxic water. Surprisingly, the sediment phosphorus release increased, showing that feedbacks between phosphorus release and oxygen depletion can be hard to break.
                                            
                                            
                                        Sebastiaan J. van de Velde, Rebecca K. James, Ine Callebaut, Silvia Hidalgo-Martinez, and Filip J. R. Meysman
                                    Biogeosciences, 18, 1451–1461, https://doi.org/10.5194/bg-18-1451-2021, https://doi.org/10.5194/bg-18-1451-2021, 2021
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                                                Some 540 Myr ago, animal life evolved in the ocean. Previous research suggested that when these early animals started inhabiting the seafloor, they retained phosphorus in the seafloor, thereby limiting photosynthesis in the ocean. We studied salt marsh sediments with and without animals and found that their impact on phosphorus retention is limited, which implies that their impact on the global environment might have been less drastic than previously assumed.
                                            
                                            
                                        Martijn Hermans, Nils Risgaard-Petersen, Filip J. R. Meysman, and Caroline P. Slomp
                                    Biogeosciences, 17, 5919–5938, https://doi.org/10.5194/bg-17-5919-2020, https://doi.org/10.5194/bg-17-5919-2020, 2020
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                                                This paper demonstrates that the recently discovered cable bacteria are capable of using a mineral, known as siderite, as a source for the formation of iron oxides. This work also demonstrates that the activity of cable bacteria can lead to a distinct subsurface layer in the sediment that can be used as a marker for their activity.
                                            
                                            
                                        Torben Windirsch, Guido Grosse, Mathias Ulrich, Lutz Schirrmeister, Alexander N. Fedorov, Pavel Y. Konstantinov, Matthias Fuchs, Loeka L. Jongejans, Juliane Wolter, Thomas Opel, and Jens Strauss
                                    Biogeosciences, 17, 3797–3814, https://doi.org/10.5194/bg-17-3797-2020, https://doi.org/10.5194/bg-17-3797-2020, 2020
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                                                To extend the knowledge on circumpolar deep permafrost carbon storage, we examined two deep permafrost deposit types (Yedoma and alas) in central Yakutia. We found little but partially undecomposed organic carbon as a result of largely changing sedimentation processes. The carbon stock of the examined Yedoma deposits is about 50 % lower than the general Yedoma domain mean, implying a very hetererogeneous Yedoma composition, while the alas is approximately 80 % below the thermokarst deposit mean.
                                            
                                            
                                        Anna Plass, Christian Schlosser, Stefan Sommer, Andrew W. Dale, Eric P. Achterberg, and Florian Scholz
                                    Biogeosciences, 17, 3685–3704, https://doi.org/10.5194/bg-17-3685-2020, https://doi.org/10.5194/bg-17-3685-2020, 2020
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                                                We compare the cycling of Fe and Cd in sulfidic sediments of the Peruvian oxygen minimum zone. Due to the contrasting solubility of their sulfide minerals, the sedimentary Fe release and Cd burial fluxes covary with spatial and temporal distributions of H2S. Depending on the solubility of their sulfide minerals, sedimentary trace metal fluxes will respond differently to ocean deoxygenation/expansion of H2S concentrations, which may change trace metal stoichiometry of upwelling water masses.
                                            
                                            
                                        Biqing Zhu, Manuel Kübler, Melanie Ridoli, Daniel Breitenstein, and Martin H. Schroth
                                    Biogeosciences, 17, 3613–3630, https://doi.org/10.5194/bg-17-3613-2020, https://doi.org/10.5194/bg-17-3613-2020, 2020
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                                                We provide evidence that the greenhouse gas methane (CH4) is enclosed in calcareous glacier-forefield sediments across Switzerland. Geochemical analyses confirmed that this ancient CH4 has its origin in the calcareous parent bedrock. Our estimate of the total quantity of CH4 enclosed in sediments across Switzerland indicates a large CH4 mass (~105 t CH4). We produced evidence that CH4 is stable in its enclosed state, but additional experiments are needed to elucidate its long-term fate.
                                            
                                            
                                        Matteo Puglini, Victor Brovkin, Pierre Regnier, and Sandra Arndt
                                    Biogeosciences, 17, 3247–3275, https://doi.org/10.5194/bg-17-3247-2020, https://doi.org/10.5194/bg-17-3247-2020, 2020
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                                                A reaction-transport model to assess the potential non-turbulent methane flux from the East Siberian Arctic sediments to water columns is applied here. We show that anaerobic oxidation of methane (AOM) is an efficient filter except for high values of sedimentation rate and advective flow, which enable considerable non-turbulent steady-state methane fluxes. Significant transient methane fluxes can also occur during the building-up phase of the AOM-performing biomass microbial community.
                                            
                                            
                                        Kyle Delwiche, Junyao Gu, Harold Hemond, and Sarah P. Preheim
                                    Biogeosciences, 17, 3135–3147, https://doi.org/10.5194/bg-17-3135-2020, https://doi.org/10.5194/bg-17-3135-2020, 2020
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                                                In this study, we investigate whether bubbles transport sediments containing arsenic and cyanobacteria from the bottom to the top of a polluted lake. We measured arsenic and cyanobacteria from bubble traps in the lake and from an experimental bubble column in the laboratory. We found that bubble transport was not an important source of arsenic in the surface waters but that bubbles could transport enough cyanobacteria to the surface to exacerbate harmful algal blooms.
                                            
                                            
                                        Nathaniel Kemnitz, William M. Berelson, Douglas E. Hammond, Laura Morine, Maria Figueroa, Timothy W. Lyons, Simon Scharf, Nick Rollins, Elizabeth Petsios, Sydnie Lemieux, and Tina Treude
                                    Biogeosciences, 17, 2381–2396, https://doi.org/10.5194/bg-17-2381-2020, https://doi.org/10.5194/bg-17-2381-2020, 2020
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                                                Our paper shows how sedimentation in a very low oxygen setting provides a unique record of environmental change. We look at the past 250 years through the filter of sediment accumulation via radioisotope dating and other physical and chemical analyses of these sediments. We conclude, remarkably, that there has been very little change in net sediment mass accumulation through the past 100–150 years, yet just prior to 1900  CE, sediments were accumulating at 50 %–70 % of today's rate.
                                            
                                            
                                        Dario Fussmann, Avril Jean Elisabeth von Hoyningen-Huene, Andreas Reimer, Dominik Schneider, Hana Babková, Robert Peticzka, Andreas Maier, Gernot Arp, Rolf Daniel, and Patrick Meister
                                    Biogeosciences, 17, 2085–2106, https://doi.org/10.5194/bg-17-2085-2020, https://doi.org/10.5194/bg-17-2085-2020, 2020
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                                                Dolomite (CaMg(CO3)2) is supersaturated in many aquatic settings (e.g., seawater) on modern Earth but does not precipitate directly from the fluid, a fact known as the dolomite problem. The widely acknowledged concept of dolomite precipitation involves microbial extracellular polymeric substances (EPSs) and anoxic conditions as important drivers. In contrast, results from Lake Neusiedl support an alternative concept of Ca–Mg carbonate precipitation under aerobic and alkaline conditions.
                                            
                                            
                                        Aurèle Vuillemin, André Friese, Richard Wirth, Jan A. Schuessler, Anja M. Schleicher, Helga Kemnitz, Andreas Lücke, Kohen W. Bauer, Sulung Nomosatryo, Friedhelm von Blanckenburg, Rachel Simister, Luis G. Ordoñez, Daniel Ariztegui, Cynthia Henny, James M. Russell, Satria Bijaksana, Hendrik Vogel, Sean A. Crowe, Jens Kallmeyer, and the Towuti Drilling Project
Science team
                                    Biogeosciences, 17, 1955–1973, https://doi.org/10.5194/bg-17-1955-2020, https://doi.org/10.5194/bg-17-1955-2020, 2020
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                                                Ferruginous lakes experience restricted primary production due to phosphorus trapping by ferric iron oxides under oxic conditions. We report the presence of large crystals of vivianite, a ferrous iron phosphate, in sediments from Lake Towuti, Indonesia. We address processes of P retention linked to diagenesis of iron phases. Vivianite crystals had light Fe2+ isotope signatures and contained mineral inclusions consistent with antecedent processes of microbial sulfate and iron reduction.
                                            
                                            
                                        Sonja Geilert, Patricia Grasse, Kristin Doering, Klaus Wallmann, Claudia Ehlert, Florian Scholz, Martin Frank, Mark Schmidt, and Christian Hensen
                                    Biogeosciences, 17, 1745–1763, https://doi.org/10.5194/bg-17-1745-2020, https://doi.org/10.5194/bg-17-1745-2020, 2020
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                                                Marine silicate weathering is a key process of the marine silica cycle; however, its controlling processes are not well understood. In the Guaymas Basin, silicate weathering has been studied under markedly differing ambient conditions. Environmental settings like redox conditions or terrigenous input of reactive silicates appear to be major factors controlling marine silicate weathering. These factors need to be taken into account in future oceanic mass balances of Si and in modeling studies.
                                            
                                            
                                        Jessica B. Volz, Laura Haffert, Matthias Haeckel, Andrea Koschinsky, and Sabine Kasten
                                    Biogeosciences, 17, 1113–1131, https://doi.org/10.5194/bg-17-1113-2020, https://doi.org/10.5194/bg-17-1113-2020, 2020
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                                                Potential future deep-sea mining of polymetallic nodules at the seafloor is expected to severely harm the marine environment. However, the consequences on deep-sea ecosystems are still poorly understood. This study on surface sediments from man-made disturbance tracks in the Pacific Ocean shows that due to the removal of the uppermost sediment layer and thereby the loss of organic matter, the geochemical system in the sediments is disturbed for millennia before reaching a new equilibrium.
                                            
                                            
                                        Ralf Conrad, Melanie Klose, and Alex Enrich-Prast
                                    Biogeosciences, 17, 1063–1069, https://doi.org/10.5194/bg-17-1063-2020, https://doi.org/10.5194/bg-17-1063-2020, 2020
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                                                Lake sediments release the greenhouse gas CH4. Acetate is an important precursor. Although Amazonian lake sediments all contained acetate-consuming methanogens, measurement of the turnover of labeled acetate showed that some sediments converted acetate not to CH4 plus CO2, as expected, but only to CO2. Our results indicate the operation of acetate-oxidizing microorganisms couples the oxidation process to syntrophic methanogenic partners and/or to the reduction of organic compounds.
                                            
                                            
                                        Jens Rassmann, Eryn M. Eitel, Bruno Lansard, Cécile Cathalot, Christophe Brandily, Martial Taillefert, and Christophe Rabouille
                                    Biogeosciences, 17, 13–33, https://doi.org/10.5194/bg-17-13-2020, https://doi.org/10.5194/bg-17-13-2020, 2020
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                                                In this paper, we use a large set of measurements made using in situ and lab techniques to elucidate the cause of dissolved inorganic carbon fluxes in sediments from the Rhône delta and its companion compound alkalinity, which carries the absorption capacity of coastal waters with respect to atmospheric CO2. We show that sediment processes (sulfate reduction, FeS precipitation and accumulation) are crucial in generating the alkalinity fluxes observed in this study by in situ incubation chambers.
                                            
                                            
                                        Sophie A. L. Paul, Matthias Haeckel, Michael Bau, Rajina Bajracharya, and Andrea Koschinsky
                                    Biogeosciences, 16, 4829–4849, https://doi.org/10.5194/bg-16-4829-2019, https://doi.org/10.5194/bg-16-4829-2019, 2019
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                                                We studied the upper 10 m of deep-sea sediments, including pore water, in the Peru Basin to understand small-scale variability of trace metals. Our results show high spatial variability related to topographical variations, which in turn impact organic matter contents, degradation processes, and trace metal cycling. Another interesting finding was the influence of dissolving buried nodules on the surrounding sediment and trace metal cycling.
                                            
                                            
                                        Sarah Paradis, Antonio Pusceddu, Pere Masqué, Pere Puig, Davide Moccia, Tommaso Russo, and Claudio Lo Iacono
                                    Biogeosciences, 16, 4307–4320, https://doi.org/10.5194/bg-16-4307-2019, https://doi.org/10.5194/bg-16-4307-2019, 2019
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                                                Chronic deep bottom trawling in the Gulf of Castellammare (SW Mediterranean) erodes large volumes of sediment, exposing over-century-old sediment depleted in organic matter. Nevertheless, the arrival of fresh and nutritious sediment recovers superficial organic matter in trawling grounds and leads to high turnover rates, partially and temporarily mitigating the impacts of bottom trawling. However, this deposition is ephemeral and it will be swiftly eroded by the passage of the next trawler.
                                            
                                            
                                        Zhichao Zhou, Bo Liang, Li-Ying Wang, Jin-Feng Liu, Bo-Zhong Mu, Hojae Shim, and Ji-Dong Gu
                                    Biogeosciences, 16, 4229–4241, https://doi.org/10.5194/bg-16-4229-2019, https://doi.org/10.5194/bg-16-4229-2019, 2019
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                                                This study shows a core bacterial microbiome with a small proportion of shared operational taxonomic units of common sequences among all oil reservoirs. Dominant methanogenesis shifts from the hydrogenotrophic pathway in water phase to the acetoclastic pathway in the oil phase at high temperatures, but the opposite is true at low temperatures. There are also major functional metabolism differences between the two phases for amino acids, hydrocarbons, and carbohydrates.
                                            
                                            
                                        Annika Fiskal, Longhui Deng, Anja Michel, Philip Eickenbusch, Xingguo Han, Lorenzo Lagostina, Rong Zhu, Michael Sander, Martin H. Schroth, Stefano M. Bernasconi, Nathalie Dubois, and Mark A. Lever
                                    Biogeosciences, 16, 3725–3746, https://doi.org/10.5194/bg-16-3725-2019, https://doi.org/10.5194/bg-16-3725-2019, 2019
                            Hanni Vigderovich, Lewen Liang, Barak Herut, Fengping Wang, Eyal Wurgaft, Maxim Rubin-Blum, and Orit Sivan
                                    Biogeosciences, 16, 3165–3181, https://doi.org/10.5194/bg-16-3165-2019, https://doi.org/10.5194/bg-16-3165-2019, 2019
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                                                Microbial iron reduction participates in important biogeochemical cycles. In the last decade iron reduction has been observed in many aquatic sediments below its classical zone, in the methane production zone, suggesting a link between the two cycles. Here we present evidence for microbial iron reduction in the methanogenic depth of the oligotrophic SE Mediterranean continental shelf using mainly geochemical and microbial sedimentary profiles and suggest possible mechanisms for this process.
                                            
                                            
                                        Haoyi Yao, Wei-Li Hong, Giuliana Panieri, Simone Sauer, Marta E. Torres, Moritz F. Lehmann, Friederike Gründger, and Helge Niemann
                                    Biogeosciences, 16, 2221–2232, https://doi.org/10.5194/bg-16-2221-2019, https://doi.org/10.5194/bg-16-2221-2019, 2019
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                                                How methane is transported in the sediment is important for the microbial community living on methane. Here we report an observation of a mini-fracture that facilitates the advective gas transport of methane in the sediment, compared to the diffusive fluid transport without a fracture. We found contrasting bio-geochemical signals in these different transport modes. This finding can help to fill the gap in the fracture network system in modulating methane dynamics in surface sediments.
                                            
                                            
                                        Laura A. Casella, Sixin He, Erika Griesshaber, Lourdes Fernández-Díaz, Martina Greiner, Elizabeth M. Harper, Daniel J. Jackson, Andreas Ziegler, Vasileios Mavromatis, Martin Dietzel, Anton Eisenhauer, Sabino Veintemillas-Verdaguer, Uwe Brand, and Wolfgang W. Schmahl
                                    Biogeosciences, 15, 7451–7484, https://doi.org/10.5194/bg-15-7451-2018, https://doi.org/10.5194/bg-15-7451-2018, 2018
                                    Short summary
                                    Short summary
                                            
                                                Biogenic carbonates record past environmental conditions. Fossil shell chemistry and microstructure change as metastable biogenic carbonates are replaced by inorganic calcite. Simulated diagenetic alteration at 175 °C of different shell microstructures showed that (nacreous) shell aragonite and calcite were partially replaced by coarse inorganic calcite crystals due to dissolution–reprecipitation reactions. EBSD maps allowed for qualitative assessment of the degree of diagenetic overprint.
                                            
                                            
                                        Wytze K. Lenstra, Matthias Egger, Niels A. G. M. van Helmond, Emma Kritzberg, Daniel J. Conley, and Caroline P. Slomp
                                    Biogeosciences, 15, 6979–6996, https://doi.org/10.5194/bg-15-6979-2018, https://doi.org/10.5194/bg-15-6979-2018, 2018
                                    Short summary
                                    Short summary
                                            
                                                We show that burial rates of phosphorus (P) in an estuary in the northern Baltic Sea are very high. We demonstrate that at high sedimentation rates, P retention in the sediment is related to the formation of vivianite. With a reactive transport model, we assess the sensitivity of sedimentary vivianite formation. We suggest that enrichments of iron and P in the sediment are linked to periods of enhanced riverine input of Fe, which subsequently strongly enhances P burial in coastal sediments.
                                            
                                            
                                        Jiarui Liu, Gareth Izon, Jiasheng Wang, Gilad Antler, Zhou Wang, Jie Zhao, and Matthias Egger
                                    Biogeosciences, 15, 6329–6348, https://doi.org/10.5194/bg-15-6329-2018, https://doi.org/10.5194/bg-15-6329-2018, 2018
                                    Short summary
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                                                Our work provides new insights into the biogeochemical cycling of iron, methane and phosphorus. We found that vivianite, an iron-phosphate mineral, is pervasive in methane-rich sediments, suggesting that iron reduction at depth is coupled to phosphorus and methane cycling on a much greater spatial scale than previously assumed. Acting as an important burial mechanism for iron and phosphorus, vivianite authigenesis may be an under-considered process in both modern and ancient settings alike.
                                            
                                            
                                        Marc A. Besseling, Ellen C. Hopmans, R. Christine Boschman, Jaap S. Sinninghe Damsté, and Laura Villanueva
                                    Biogeosciences, 15, 4047–4064, https://doi.org/10.5194/bg-15-4047-2018, https://doi.org/10.5194/bg-15-4047-2018, 2018
                                    Short summary
                                    Short summary
                                            
                                                Benthic archaea comprise a significant part of the total prokaryotic biomass in marine sediments. Here, we compared the archaeal diversity and intact polar lipid (IPL) composition in both surface and subsurface sediments with different oxygen regimes in the Arabian Sea oxygen minimum zone. The oxygenated sediments were dominated by Thaumarchaeota and IPL-GDGT-0. The anoxic sediment contained highly diverse archaeal communities and high relative abundances of IPL-GDGT-1 to -4.
                                            
                                            
                                        Georgina Robinson, Thomas MacTavish, Candida Savage, Gary S. Caldwell, Clifford L. W. Jones, Trevor Probyn, Bradley D. Eyre, and Selina M. Stead
                                    Biogeosciences, 15, 1863–1878, https://doi.org/10.5194/bg-15-1863-2018, https://doi.org/10.5194/bg-15-1863-2018, 2018
                                    Short summary
                                    Short summary
                                            
                                                This study examined the effect of adding carbon to a sediment-based effluent treatment system to treat nitrogen-rich aquaculture waste. The research was conducted in incubation chambers to measure the exchange of gases and nutrients across the sediment–water interface and examine changes in the sediment microbial community. Adding carbon increased the amount of nitrogen retained in the treatment system, thereby reducing the levels of nitrogen needing to be discharged to the environment.
                                            
                                            
                                        Daniele Brigolin, Christophe Rabouille, Bruno Bombled, Silvia Colla, Salvatrice Vizzini, Roberto Pastres, and Fabio Pranovi
                                    Biogeosciences, 15, 1347–1366, https://doi.org/10.5194/bg-15-1347-2018, https://doi.org/10.5194/bg-15-1347-2018, 2018
                                    Short summary
                                    Short summary
                                            
                                                We present the result of a study carried out in the north-western Adriatic Sea by combining two different types of models with field sampling. A mussel farm was taken as a local source of perturbation to the natural flux of particulate organic carbon to the sediment. Differences in fluxes were primarily associated with mussel physiological conditions. Although restricted, these changes in particulate organic carbon fluxes induced visible effects on sediment biogeochemistry.
                                            
                                            
                                        Volker Brüchert, Lisa Bröder, Joanna E. Sawicka, Tommaso Tesi, Samantha P. Joye, Xiaole Sun, Igor P. Semiletov, and Vladimir A. Samarkin
                                    Biogeosciences, 15, 471–490, https://doi.org/10.5194/bg-15-471-2018, https://doi.org/10.5194/bg-15-471-2018, 2018
                                    Short summary
                                    Short summary
                                            
                                                We determined the aerobic and anaerobic degradation rates of land- and marine-derived organic material in East Siberian shelf sediment. Marine plankton-derived organic carbon was the main source for the oxic dissolved carbon dioxide production, whereas terrestrial organic material significantly contributed to the production of carbon dioxide under anoxic conditions. Our direct degradation rate measurements provide new constraints for the present-day Arctic marine carbon budget.
                                            
                                            
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                Short summary
                    The study presents a P budget including the P input from the water column, the P burial in the sediments, as well as the P release from the sediments. We found that the P input could not maintain the P release rates. Consideration of other P sources, e.g., terrigenous P and P released from the dissolution of Fe oxyhydroxides, showed that none of these can account for the missing P. Thus, it is likely that abundant sulfide-oxidizing bacteria release the missing P during our measurement period.
                    The study presents a P budget including the P input from the water column, the P burial in the...
                    
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